Difference between sound reduction tests and how Altro products perform | The Altro blog

Sound insulation is very important in building design, particularly in industries like healthcare, where the health and recovery of patients are proven to be better when noise stressors are reduced.

There are multiple ways to measure flooring’s sound reduction properties, and they all measure something different. The aim of this blog is to identify what these methods are as well as the differences between them.

ISO 10140 + ISO 140 is a European standard that measures reduction in footfall noise, the sound within the room. The higher the number, the quieter the floor is. This standard measures something completely different than the other two as it focuses on the sound within the room. The feature of reducing sound in the room is important in all industries but particularly with senior living and healthcare.

Impact Insulation Class or IIC for short is an important measure of sound transmission through a floor. It measures the sound transmitted from footfall noise and other impacts in the floor. An IIC rating is a number and the larger the number the better the rating. A concrete floor is the control with a rating of zero.

Minimum IIC ratings are set by the Uniform Building Code to be 50 in most condominiums and other residential areas. We see this also come up a lot in healthcare and senior living where sound insulation is important. At a rating of 50, footfall noise is quite pronounced and very audible in the unit below. In response, some cities and condominium associations have adopted laws that are more stringent. It is important to note this is for the complete floor to ceiling assembly. That means everything from the floor covering, underlayment, subfloor, and the ceiling of the floor below count towards that number. In most test conditions a default floor to ceiling assembly is used to isolate the effect that the floor covering or ceiling tile has on the rating.

STC or Sound Transmission Class: Sound Transmission Class (STC) in flooring is a rating of how well an assembly reduces airborne sound from a room above to the room below. So for example a loud television or a dog barking.

This is a method for determining airborne sound transmission loss between 125 Hz and 4,000 Hz. This range covers the majority of common noises we hear including speech, television, music, dogs barking, and other similar annoyances. A higher STC rating often shows improved performance. However, the sound rating is essentially an average over the 16 frequency points tested.

Generally a rating of 45 and above is preferred, but it also depends on the assembly used (subfloor, floor covering, underlayment, drop ceiling, etc).